每个进程的最大线程数 - 的sysconf（_SC_THREAD_THREADS_MAX）失败 [英] Maximum number of threads per process - sysconf(_SC_THREAD_THREADS_MAX) failing

问题描述

我试图找到一个UNIX机器上的每个进程的最大线程数，并写了下面的code使用的sysconf：

I'm trying to find the maximum number of threads per process on a UNIX machine and wrote the code below to use sysconf:

#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

int main() {
errno = 0;
long maxThreads = sysconf(_SC_THREAD_THREADS_MAX);
if (maxThreads == -1 && errno == 0)
{
    printf("the variable corresponding to _SC_THREAD_THREADS_MAX "
            "is associated with functionality that is not "
            "supported by the system\n");
    exit(1);
}
if (maxThreads == -1)
{
    printf("errno: %d\n", errno);
    exit(1);
}

printf ("max num threads per process: %ld\n", maxThreads);

exit(0);
}

可惜的sysconf（）返回-1不改变错误号！有谁知道如何解决这个问题，最终是什么每个进程Pthreads中的最大值是多少？
谢谢

Unfortunately the sysconf() returns -1 without changing the errno! Does anyone know how to get around this problem and eventually what is the maximum number of Pthreads per process? Thanks

P.S。我试了一下Solaris和Linux上，得到了相同的结果。然而HPUX做回8000！

P.S. I tried it on Solaris and Linux and got the same result. However HPUX did return 8000!

推荐答案

据我的手册的sysconf 在我的Mac OSX 10.7.X：

According to my manual for sysconf on my Mac OSX 10.7.X:

如果调用的sysconf（）不成功，返回-1，并errno设置为合适。否则，如果变量与不支持的功能相关，则返回-1，并将errno不被修改。否则，当前变量的值返回。

If the call to sysconf() is not successful, -1 is returned and errno is set appropriately. Otherwise, if the variable is associated with functionality that is not supported, -1 is returned and errno is not modified. Otherwise, the current variable value is returned.

在linux下它是不同的：

Under linux it is different:

如果名称是无效的，则返回-1，并设置errno为EINVAL。否则，返回的值是系统资源和errno的值不改变。在选项的情况下，如果查询选项可用，则返回一个正值，-1，如果它不是。在极限的情况下，-1意味着没有明确的限制。

If name is invalid, -1 is returned, and errno is set to EINVAL. Otherwise, the value returned is the value of the system resource and errno is not changed. In the case of options, a positive value is returned if a queried option is available, and -1 if it is not. In the case of limits, -1 means that there is no definite limit.

因此​​，它看起来像 _SC_THREAD_THREADS_MAX 不在这个架构有效sysconfig中的变量或者是没有限制的。或者，也许有对另一个定义-1 其它架构。你必须检查你试图去上班每种架构的手册。

So it looks like that _SC_THREAD_THREADS_MAX is not a valid sysconfig variable on that architecture or maybe there is no limit. Or maybe there is another definition for -1 on other architectures. You'll have to check the manual on each architecture you are trying to get to work.

如果 _SC_THREAD_THREADS_MAX 是无效的，那么你可能想尝试的过程，而不是线程。也许有一个最大的进程设置这也意味着最大线程数。

If _SC_THREAD_THREADS_MAX is not valid then you might want to try processes instead of threads. Maybe there is a max processes setting which also means max threads.

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